拱坝坝肩破碎基础处理探讨

拱坝是利用拱圈把水压力传递到两坝肩的一种坝型,所以拱坝对坝肩地质条件要求较高。有时由于地形地质条件限制,部分拱坝坝肩座落在断层、软弱夹层和破碎基础等基础上,为保证拱坝的安全,坝肩基础需要进行处理。现主要介绍软弱基础上坝肩的处理措施,为中低型拱坝的坝肩处理提供参考。     

复杂地质条件下拱坝坝肩抗滑稳定分析及处理研究

结合云南省德钦县丹达河水电站工程实例,运用刚体极限平衡法对右坝肩抗滑稳定进行研究,采用《混凝土拱坝设计规范》(SL 282—2003)中的公式及规定,分析认为未加固处理坝肩断层f12抗滑稳定安全系数偏低,不能满足规范要求,应进行必要处理。提出处理方案,对经过处理方案处理后的f12断层进行进一步分析,分析认为加固处理后的坝肩断层f12抗滑稳定安全系数能满足规范要求,拱肩断层f12加固处理方案有效。     

断层对孟底沟高拱坝坝肩变位及稳定性的影响研究

孟底沟水电站高拱坝由于左岸坝肩岩体受到 f1、f2、f6断层的切割,使得左坝肩形成了四个大块体。由于 f6与库水连通,若不做处理,蓄水后作用在 f6上的全水头渗压势必将使左岸坝肩岩体向河谷变形。因此左坝肩岩体变形连续性,拱坝坝体变位对称性及坝肩控制性滑块稳定性成为该工程的突出问题。充分考虑左岸坝肩断层交汇和切割关系,采用刚体弹簧元法对上述问题进行了计算分析和研究。结果表明：f6断层水压推力作用将使得断层交汇处出现不连续变形,断层产生错动现象,断层交汇点最大错动位移达到2．03 cm ,同时削弱了拱坝坝体变位对称性,左右半拱顺河向和横河向最大位移差分别为1．42 cm 和0．86 cm ;坝肩控制性滑移块体稳定安全系数下降,最大降幅可达18．19％。建议对 f6进行封堵或者置换处理,防止库水侵入山体。     

大花水水电站拦河大坝基础处理设计

大花水水电站拦河大坝为河床拱坝 左岸重力坝的组合坝型,拱坝最大坝高134.50 m,是目前国内外在建最高的碾压混凝土拱坝;重力坝坝高73 m,作为拱坝上部的坝肩。该工程拦河大坝坝址区地质结构较为复杂,其基础处理设计显得尤为突出,本文重点介绍该工程拦河大坝基础处理及右岸坝肩的断层处理设计。     

江口水电站岩溶地区断层溶洞部位的施工处理

江口水电站坝址属岩溶地区，地质条件复杂、断层、风化带、溶洞等地质现象普遍分布于坝基坝肩，对大坝的稳定安全运行影响较大。文章针对江口工程所出现的地质问题，右坝肩断层与溶洞交汇处部位采用混凝土置换回填、其相应坝段采用铺设钢筋、加强振捣及高压灌浆等手段施工处理后，满足了大坝的安全稳定要求。     

锦屏高拱坝三维非线性有限元稳定分析

高拱坝坝肩的稳定性是拱坝结构安全运行的基础,锦屏高拱坝坝址区左右坝肩存在几条规模较大的断层、深部节理裂隙、层间挤压错动带、低波速带、岩体风化、卸荷等不良地质结构,因此,坝肩稳定性成为锦屏高拱坝设计中的重大技术问题.运用三维非线性有限元分析方法,对锦屏高拱坝坝肩加固处理前后的稳定性进行了分析对比研究,揭示了边坡失稳的可能形式、部位及规模,并据此对边坡的稳定性进行分析与评价.计算结果表明,锦屏高拱坝加固处理是合理的,满足大坝的稳定要求.     

温泉水库右坝肩断层防渗帷幕灌浆

详细介绍了温泉水库右坝肩断层部位的防渗帷幕灌浆设计、施工及其效果.     

拱坝基础处理设计中两个问题的探讨

本文叙述了一个在建中177米高的重力拱坝的一些主要基础问题。由于受到多次构造运动和其它地质因素影响,两岸坝肩被8条大断层和4组裂隙相互交切,使坝肩岩体的完整性受到一定程度的破坏。 在这种地质条件及其它一些不利的地形情况下建造重力拱坝,要十分慎重。文中扼要叙述了我们在设计该坝过程中,对坝肩抗滑稳定和深层断层特殊处理这两个问题所做的一些考虑和初步探讨。通过计算、试验研究和分析,本坝地质条件虽复杂,但只要继续进行仔细的工程处理和研究,坝肩抗滑稳定和变位情况是能满足将来大坝安全运行要求的。     

乌二水电站左坝肩绕坝渗流计算及处理措施

水库蓄水后,由于上下游水头差,使库水沿坝两岸岩石的空隙、裂隙、溶洞、断层等向坝下游渗漏,一般称为绕坝渗漏又称坝肩渗漏。绕坝渗漏的分析计算及处理,对保证水库的安全运行和提高工程效益具有重要的现实意义。文章通过对乌二水电站左坝肩绕坝渗流处理方案分析,选取柱列式混凝土防渗墙作为防渗处理措施。     

江口水电站拱坝坝肩三维抗滑稳定分析

对于混凝土拱坝,坝肩三维抗滑稳定是拱坝设计中较为突出的问题。本文采用刚体极限平衡法计算了江口水电站G断层拱坝坝肩王维抗滑稳定,该法简单易行,精度较高,节省计算时间。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.